You mean the Hercules Terra tracs? It really was since then that it went down to that.

 

Tires can definitely hurt or help mileage. However it may not be as bad as you think. Did you upsize from your previous tires to these? A larger tire travels more distance in one rotation which will cause your speedometer to read lower than your actual speed and the odometer to show less mileage. If you did change tire size getting your speedometer recalibrated will get you an accurate calculation, the superchips tuners are capable of this but that's an expensive buy only for tire size. They are a great boost overall though.

 

The tire size is exactly the same, 265/65/17, but they have a much more aggressive tread. They also might be a little deflated.

It has gone up since I last looked, from 10.1 to 10.8...so I'm hoping that it does just need a bit of time, maybe a month, to give me a fair indication.

 

I assume others have noticed creeks and groans from the truck as the weather gets colder and colder? It is about -8 celsius here and the back end of my truck is starting to make a loud creak going over very small bumps.

Mostly goes away once the truck warms up though.